Although communication systems take many forms, the general purpose of a communication system is to transmit information from a source to a destination located some distance away. As a result, communication systems basically consist of a transmitter, a channel and a receiver. The function of the transmitter is to process some original message (i.e. information to be communicated) into a form suitable for transmission over the channel. The channel, in turn, provides a physical connection between the transmitter and the receiver so that the message can be communicated therebetween. The receiver, therefor, has the function of processing the received signal and reproduce the original message.
Before transmitting the original message, however, the transmitter must manipulate the original message into a form suitable for transmission over the channel. The process of manipulating the original message into a transmission signal is called modulation. In general, modulation involves varying some parameter of a carrier wave with the message signal in such a way that the spectrum of the modulated wave matches the bandwidth of the channel over which the message is communicated. Once modulated, the signal is transmitted over the channel to the receiver, which, as stated above, recreates the original signal from the modulated signal. This process is called demodulation. As a result, communications systems can be said to transmit information through a series of modulation/demodulation processes over the channel.
Heretofore, wireless communications systems are configured to transmit packet data from a transmitting unit to a receiving unit over a single dedicated channel. That is, in packet data wireless systems the transmitting unit and receiving unit communicate over a single channel dedicated to the transmission of data. This configuration was developed to reduce software and hardware complexity at the terminal and network side, as well as minimize possible disruption to any incumbent voice communication system. Thus, the overall data rate of such present day system is limited to the data rate supported by that given single channel.
With the advent of more varied and customized wireless user services, such present day systems have come under pressure to provide ever increasing bit rates. Moreover, those skilled in the art have found that such present day systems do not adequately provide the desired services (i.e. bit rates) without sacrificing system performance and efficiency. Thus, there is a need for a wireless packet data communication system that enables high-rate packet data communications between communicating units, without sacrificing system performance and efficiency.